Exemplary embodiments of this invention generally relate to ducts and, more particularly, to fittings configured for use with re-enforced thermoplastic ducts.
In conventional duct assemblies, when a portion of a fitting or coupling is inserted into an end of a flexible duct, the material of the duct stretches around barbs of the fitting. Because the deformation of the duct is elastic, when the fitting is removed, the duct will return to its original size. When the duct stretches to receive the fitting, the compressive force of the duct material against the barbed surface of the fitting holds the fitting in position.
Flexible synthetic ducts, such as those made from synthetic rubber, are susceptible to deterioration as a result of heat, and permeability by the fluid conveyed through the duct, as well as other failures. As such, reinforced hoses or ducts constructed from thermoplastic materials, such as reinforced thermoplastic, for example, are being used in applications where flexible synthetic ducts are not suitable. A thermoplastic duct used in an aircraft must meet specific smoke, toxicity, and chemical requirements. Additional requirements of a duct configured for use on an aircraft are especially stringent because the operating environment of the duct may range from a hot and humid atmosphere, such as when the aircraft is on the ground, to a freezing, low pressure atmosphere when the aircraft is at extremely high altitudes. Ducts formed from reinforced thermoplastics, however, are difficult to couple and seal with conventional couplings and fittings because of the rigid nature of the thermoplastic material.